Mtn must refund me

I had contract with Mtn, September 2021 I decided to pay it(settle) to reduce my debts, I called Mtn to find out how much I must pay they said I must pay R3000 and some change, I paid that amount and called them to cancel and let me use my number cz thats the only number I have, I struggled for more than 7 days, I was unable to make call only thier number which I called daily to ask them to help me, they ended up sorting that after fighting, adking them whay must I do, 15 October, I received statement saying there's is an amount of R1800 tha is on credit, I emailed them asking about this amount, they said I paid more than I was expected, so they will refund me, they asked for bank confirmation on the 27th of October 2021,when I called they said they won't refund me😥😥😥, I even have emails whete they were saying I paid more than I was expected to pay, they will refund me all of a sudden they wont pay, Iam ****ed how can they do such, I really need this money,